JP3500999B2 - Vehicle engine start control method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine start control method for a vehicle such as an automobile, and more particularly to a hybrid vehicle equipped with an engine and a motor as a driving force source for the vehicle, or to automatically stop the engine during idling. The present invention relates to a vehicle engine start control method suitable for automatically starting an engine in an idle stop vehicle.

[0002]

2. Description of the Related Art As a technique relating to automatic engine starting from running of a motor in a hybrid vehicle equipped with an engine and a motor as a power source of the vehicle, for example, Japanese Patent Laid-Open No. 6-17.
The technique described in Japanese Patent No. 727 is known. In this conventional example, an engine is connected to a motor directly connected to a drive system of a vehicle via a clutch, and when the engine is started from traveling by the motor alone, the clutch is connected and the output of the motor is increased. In this way, the shock is prevented from occurring when the engine is started.

[0003]

However, in the above-mentioned conventional example, when a part of the output of the motor is consumed for starting the engine at the time of automatic engine start, the phenomenon in which the vehicle driving torque drops is increased by increasing the output of the motor. However, there is a problem that the shocks generated before and after the start of engine combustion cannot be sufficiently suppressed.

That is, in the above-mentioned conventional example, under the condition that the clutch is engaged and the engine starts to rotate, the engine produces a contract torque which is a resistance against the running of the vehicle, but from this state, the combustion of the engine is started. Then, the engine generates a so-called positive torque that contributes to the running of the vehicle, which causes a problem that a shock is generated due to a sudden torque step.

This shock may be transmitted to the vehicle body through the drive system of the vehicle and may give an occupant an unpleasant feeling. Particularly, the start of combustion of the engine, which causes such a shock, is not generated by the driver's conscious operation, and thus the shock as described above is easily felt by the driver.

Further, although the shock at the time of automatic engine starting in an idle stop vehicle is not much different from the shock at the time of starting by key operation, the shock at the time of automatic engine starting which is not due to the driver's conscious operation is felt very much. In that respect, there is a problem similar to that of the hybrid vehicle described above.

Therefore, an object of the present invention is to provide an engine start control method for a vehicle which can suppress the occurrence of shock when the engine is started.

[0008]

According to a first aspect of the present invention, there is provided an engine start control method for a vehicle, wherein the engine is automatically started without key operation by a driver. The engine is set to the compression lean operation mode, and the fuel injection timing and ignition timing are set at the start of fuel supply.
Within the region where stable combustion of the engine is possible and the net average
Operate with a delay so that the effective pressure becomes low . As shown in FIG. 2, the engine during compression lean operation can steadily burn without misfire by delaying the fuel injection timing and the ignition timing.
In the present invention, the fuel is directly injected into the combustion chamber during the compression stroke to operate the engine with a lean air-fuel ratio, so that the engine can be stably started to burn with an extremely small amount of fuel, and the engine at the time of starting combustion Since the output can be suppressed, it is possible to suppress the occurrence of shock at the start of engine combustion. Since both the combustion injection timing and the ignition timing at the start of combustion of the engine are delayed, the output torque of the engine at the start of combustion can be suppressed more effectively. Therefore, it is possible to more reliably suppress the occurrence of shock.

As a preferred aspect of the present invention, it is desirable to apply the present invention to a hybrid vehicle equipped with an engine and a motor as a driving force source of the vehicle when the engine is automatically started while the vehicle is running. In this case, a torque step is likely to occur, so that the shock suppressing effect is enhanced.

[0010]

A preferred embodiment of the present invention is set forth in claim 2.
Operated in the compression lean mode of operation as described
After that, advance the fuel injection timing and ignition timing, and then
It is desirable to gradually increase the output torque of the engine by switching to the uniform combustion operation mode . In this case, the shock given to the occupant at the start of combustion of the engine can be suppressed, and the acceleration can be smoothly shifted.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIGS.

A vehicle which runs by combining an engine as an internal combustion engine and a motor, a so-called hybrid vehicle 1, is shown in FIG.
As shown in FIG. 2, a spark ignition type engine 2, a motor / generator 3 that functions as a motor and a generator, wheels 4 and 4 as driving wheels, and an accelerator opening degree detection means 5.
A vehicle speed detection means 6, an engine speed detection means 7, a crank angle detection means 16, a key switch 22, an ECU (Electronic Control Unit) 8 as a control means, and the like are provided.

The engine 2 is provided with an injector 10 as a fuel injection means for directly injecting fuel into its combustion chamber. The injector 10 is configured to be able to directly inject fuel into the combustion chamber of the engine 2. The injector 10 is configured such that the injection amount of fuel per unit time is substantially constant, and the injection time is controlled by the ECU 8 or the like to control the amount of fuel injected into the combustion chamber.

The engine 2 operates in a compression lean operation mode in which fuel is directly injected from the injector 10 into the combustion chamber during the compression stroke and operates at a predetermined lean air-fuel ratio (30 to 50), and into the combustion chamber during the intake stroke. A uniform combustion operation mode in which fuel is supplied and the air-fuel ratio (12 to 23) that is richer than that in the compression lean operation mode is operated can be switched.

Further, the engine 2 is provided with an ignition device 9, and the ignition timing of the engine 2 is controlled by controlling the operation timing thereof by the aforementioned ECU 8.

The output shaft 11 of the engine 2 is connected to the motor / generator 3 via the clutch 12. The operation of the clutch 12 is controlled by the above-mentioned ECU 8, and the transmission of power between the engine 2 and the motor / generator 3 is brought into and out of contact with the clutch 12. The engine 2 and the motor / generator 3 are connected to the axle 14 and the pair of left and right wheels 4 and 4 via a differential gear 13 and the like.

Further, a starting clutch 21 is provided between the motor / generator 3 and the differential gear 13, and the starting clutch 21 is normally in a contact state and the engine 2 is stopped or the engine is stopped. 2 At the time of starting, it will be in a disconnection state. The wheels 4, 4, the differential gear 13, and the axle 14 form the drive system members described in this specification.

The motor / generator 3 has the functions of both an electric motor and a generator. When it functions as an electric motor, it drives the wheels 4, 4 via the differential gear 13 and the axle 14. At the same time, when it functions as a generator, the driving force transmitted from the engine 2, the axle 14, or the like is used to generate power to charge a battery (not shown).

The accelerator opening detecting means 5 detects the on / off operation and the operation amount of the accelerator pedal, and outputs an accelerator opening signal Ac to the ECU 8. The vehicle speed detection means 6 is a known vehicle speed sensor or the like that can detect rotation of the wheels 4 and the like, and outputs a vehicle speed signal Vs toward the ECU 8. The engine speed detecting means 7 detects the speed of the crankshaft of the engine 2 and outputs an engine speed signal Ne to the ECU 8. Crank angle detecting means 16
Detects a crank angle of the engine 2 within a range of 720 degrees from the crank shaft angle and the cam shaft angle, and outputs a crank angle signal Ca to the ECU 8. Also, key switch 2
2 is an engine start request signal Ky by a driver's key operation
To detect.

The ECU 8 controls the above-mentioned signals Ac, Vs, N.
Based on e, Ca, Ky, etc., the operations of the motor / generator 3, the ignition device 9, the clutch 12, the starting clutch 21, the injector 10, etc. are controlled.

First, an outline of the starting control for the engine 2 will be described. When the ECU 8 makes a request to start the engine 2 based on the operation of the key switch 22, that is, when the driver makes a request to start the engine 2. , The engine 2 is started in the uniform combustion operation mode with priority given to the startability of the engine 2. Further, when the ECU 8 automatically requests the engine start regardless of the operation of the key switch 22, that is, when the engine is automatically started regardless of the driver's conscious operation, the shock control at the start is suppressed. Start the engine in compression lean operation mode with priority.

Next, details of the case where the engine is automatically started will be described.

As for the ECU 8, the hybrid vehicle 1 is a motor / motor.
The injector 10 is controlled so as to stop the fuel injection into the combustion chamber of the engine 2 when the generator 3 can travel alone, when the engine 2 is decelerated even when the engine 2 is operating, or when traveling on a downhill. When the fuel injection from the injector 10 is stopped, the ECU 8 operates the engine 2 with the clutch 12
To separate from the drive system member. Then, the vehicle travels using only the output of the motor / generator 3 with the engine 2 stopped. In this traveling state of the motor / generator 3 alone, for example, when the accelerator pedal is operated and acceleration more than the output of the motor / generator 3 is requested, the engine 2 is connected to the drive system member by the clutch 12 and the engine is connected to the combustion chamber. The injector 10 is controlled so that the fuel supply is started, and the ignition device 9 is operated to start the engine 2.

When starting fuel injection into the combustion chamber, the ECU 8 operates the engine 2 in the compression lean operation mode described above. At this time, the ECU 8 delays at least one of the fuel injection timing and the ignition timing by comparing with an MBT advance angle described later. In the present embodiment, as shown in FIG. 2, the ECU 8 delays both the fuel injection timing and the ignition timing, and the injector 10
And the ignition device 9 is controlled.

In FIG. 2, the horizontal axis indicates the end timing of fuel injection. The injection end timing is delayed toward the left in the figure, and the injection end timing is advanced toward the right. There is. The vertical axis represents the ignition timing. The ignition timing is delayed as it goes downward in the figure, and the ignition timing is advanced as it goes upward. The injection end timing and the ignition timing indicate the rotation angle of the crankshaft.

Further, in FIG. 2, the curves Pe1, Pe2, P
e3 and Pe4 indicate the net average effective pressure corresponding to the output torque of the engine 2. These curves Pe1, Pe2, P
e3 and Pe4 increase in order.

A region R surrounded by a chain double-dashed line P in FIG.
The region where the engine 2 burns stably without misfiring during compression lean operation is shown, and the region outside this region R is a region where stable combustion is difficult because the engine 2 misfires.

When starting the engine 2, the ECU 8 first operates the accelerator pedal or the like to start the engine 2, and the accelerator opening signal A is transmitted from the accelerator opening detection means 5, as shown in FIG.
c is input and the clutch 12 connects the transmission of power between the engine 2 and the motor / generator 3. When the power transmission of the clutch 12 is connected, the crankshaft of the engine rotates together with the vehicle drive system members such as the axle 14 and the motor / generator 3.

When the clutch 12 is connected, the engine speed starts to increase and the engine speed signal Ne becomes 1 for example.
When the rotational speed N exceeds a predetermined rotational speed N such as 500 rpm, the engine 2 is in a region R in which stable combustion can be performed, and the injection end timing and the ignition timing are near a minimum value as shown in FIG. The injector 10 injects and ignites the minimum injection amount Q of fuel that can be injected at the timing indicated by the point D1 where the net average effective pressure is low.

After that, the fuel injection timing and the ignition timing are gradually advanced. The fuel injection timing and the ignition timing are shifted to the timing shown at point D2 in FIG. 2 which is earlier than the timing shown at point D1 with the passage of time, and the fuel is injected at the timing shown at point D3 in FIG. 2 earlier with the passage of time. To inject and ignite. Then, in the process of advancing the fuel injection timing and the ignition timing, the net average effective pressure gradually increases and the output torque of the engine 2 gradually increases.

A point D3 shown in FIG. 2 is a minimum ignition advance angle so-called MBT (Minimum Spark) at which the torque output from the crankshaft of the engine 2 during the compression lean operation becomes maximum.
Advance for Best Torque) This shows the timing of advance.

As described above, the ECU 8 corresponds to the fuel injection timing at the time of starting the fuel supply for starting the combustion of the engine 2.
The ignition timing is set to a predetermined retard position which is delayed from the MBT advance angle as indicated by point D1.

After that, the ECU 8 switches to the uniform combustion operation mode in which fuel is injected from the injector 10 into the combustion chamber during the intake stroke of the engine 2. After switching to the uniform combustion operation mode, the ignition timing is retarded again to suppress a rapid increase in the output torque, and thereafter, the injection amount is increased and the ignition timing is advanced to increase the output torque. It should be noted that the delay time (T in FIG. 3) from when the accelerator pedal is depressed to when the fuel injection amount is increased is within 1 second, and the responsiveness does not matter, and as shown in FIG. First, the output torque is an extremely low torque and then gradually increases, so that smooth acceleration can be obtained while suppressing the occurrence of shock.

FIG. 4 shows the results of measurement of changes in the average effective pressure corresponding to the output torque of the engine 2 with respect to changes in the pressure in the intake pipe when the combustion conditions of the engine 2 are changed.

In the measurement, the ECU described in this embodiment (hereinafter referred to as the product of the present invention) indicated by a black square in FIG.
The average effective pressure was measured when the engine 2 was burned by the combustion control method of No. 8 and in each of Comparative Examples A to D.

Comparative Example A shown by the solid line in FIG. 4 is the average effective pressure when the fuel supply to the engine 2 is stopped and the clutch 12 is engaged to rotate the engine 2 (when the engine 2 is in the motoring state). Is shown. In Comparative Example B indicated by white circles in FIG. 4, the amount of fuel in which the air-fuel mixture in the combustion chamber becomes the stoichiometric air-fuel ratio, so-called stoichio, is injected and the ignition timing is set to MBT.
The average effective pressure when advanced is shown.

A comparative example C shown by a black circle in FIG. 4 is a case where so-called ignition retard is performed in which an amount of fuel that is stoichio-fuel mixture is injected and the ignition timing is delayed within a region R in which stable combustion of the engine 2 is possible. The average effective pressure of is shown. Comparative Example D, which is indicated by a triangle in FIG. 4, has the injector 1 during the intake stroke.
0 indicates the average effective pressure when the minimum injection amount Q of fuel that can be injected is injected and the ignition is retarded.

According to FIG. 4, the difference of the present invention product from Comparative Example A (corresponding to the state before the start of combustion) is about 1/4 to 1/2 compared with Comparative Examples B to D. It's close.
Therefore, the product of the present invention is, for example, a motor / generator 3
It is clear that the step of the output torque of the engine 2 when the combustion of the engine 2 is started by operating the accelerator pedal or the like for acceleration from the state of traveling only with the output of 1 can be suppressed.

According to the present embodiment, the output torque of the engine 2 when the combustion of the engine 2 is started can be suppressed while the hybrid vehicle 1 is running only with the output of the motor / generator 3. It is possible to suppress the step of torque and suppress the occurrence of shock.

That is, in the compression lean operation mode, since fuel is injected during the compression stroke , a relatively rich fuel layer is formed in the vicinity of the spark plug in the combustion chamber. For this reason,
Stable combustion of the engine is possible even with a leaner air-fuel mixture with a smaller fuel injection amount. Therefore, the output torque of the engine 2 when the combustion of the engine 2 is started can be further suppressed, and the occurrence of shock can be suppressed.

Further, since the fuel injection end timing and the ignition timing at the start of combustion of the engine are delayed from the MBT advance angle, the output torque of the engine 2 at the time of starting the combustion of the engine 2 can be further suppressed, and the shock can be reduced. It is possible to further suppress the occurrence of

Further, after the start of combustion, the combustion injection end timing and the ignition timing are gradually advanced, so that it is possible to shift to acceleration more smoothly, and it is possible to suppress the discomfort felt by the driver. Becomes

In the above-described embodiment, the so-called hybrid vehicle 1 having the engine 2 and the motor / generator 3 is provided.
However, the present invention is not limited to the hybrid vehicle 1
Not limited to this, for example, it can be used to automatically start the engine in an idle stop vehicle in which the engine is automatically stopped at the time of idling and the accelerator pedal depression is detected to automatically start the engine.

[0045]

According to the present invention as set forth in claim 1, stable combustion of the engine is possible even if a leaner air-fuel mixture with a smaller fuel injection amount is used. Therefore, the output torque of the engine at the start of combustion can be suppressed.
Therefore, it is possible to suppress the occurrence of shock when the engine is automatically started. The present invention
Then, put the engine in the compression lean operation mode and
Since the fuel injection timing and ignition timing at the start of firing are delayed,
More reliably suppress the output torque of the engine at the start of combustion
You can Therefore, at the start of engine combustion
More reliably suppress the occurrence of shock in
It will be possible.

According to the present invention as set forth in claim 2, in addition to the effect of claim 1, it is provided to the occupant at the start of combustion of the engine.
Shock can be suppressed and acceleration is smoother
It becomes possible to shift to.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a hybrid vehicle as an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between fuel injection timing and ignition timing at the start of combustion according to the same embodiment.

FIG. 3 is a time chart showing the flow of processing at the start of combustion in the same embodiment.

FIG. 4 is a diagram showing average effective pressures of the engine of the embodiment and a comparative example.

[Explanation of symbols]

1 ... Hybrid car (vehicle) 2 ... engine 4 ... Wheel (drive system member) 13 ... Differential gear (drive system member) 14 ... Axle (drive system member) D1 ... predetermined retard position

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification FI F02D 43/00 301 F02D 43/00 301B 301E 301J F02N 11/04 F02N 11/04 D F02P 5/15 B60K 6/04 310 // B60K 6/04 310 530 530 F02P 5/15 E ZHV B60K 6/04 ZHV (72) Inventor Jun Takemura 5-3-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation (56) References Japanese Patent Laid-Open No. 10-212983 (JP, A) Japanese Patent Laid-Open No. 10-331682 (JP, A) Japanese Patent Laid-Open No. 10-141115 (JP, A) Japanese Patent Laid-Open No. 10-68341 (JP, A) Japanese Patent Laid-Open No. 6-93902 (JP , A) JP 8-291729 (JP, A) JP 6-93943 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F02D 29/02 F02D 29/02 321 F02D 17/00 F02D 41/00-45/00 B6 0K 6/02-6/04 F02N 11/04

Claims (2)

(57) [Claims] 1. A compression lean operation mode in which fuel is directly injected into a combustion chamber during a compression stroke to operate at a lean air-fuel ratio and a fuel is supplied during an intake stroke to operate at an air-fuel ratio richer than that in the compression lean operation mode. It has an engine that can be switched to the uniform combustion operation mode described above, and when the engine is automatically started without any key operation by the driver, the engine is set to the compression lean operation mode and at the time of starting fuel supply. , Fuel injection timing and ignition timing
Within the region where stable combustion of the engine is possible and the net average
A method for controlling engine start of a vehicle, comprising: driving with a retard so that the effective pressure becomes low . 2. When the engine is started automatically without any key operation by the driver, the fuel injection timing and the ignition timing are advanced after the engine is operated in the compression lean operation mode, and then the engine is advanced. 2. The engine start control method for a vehicle according to claim 1, wherein the uniform combustion operation mode is switched to.